Rotational thrombectomy wire

ABSTRACT

A rotatable thrombectomy wire for breaking up thrombus or other obstructive material comprising an inner core composed of a flexible material and an outer wire surrounding at least a portion of the inner core. The outer wire has a sinuous shaped portion at a distal region. The inner core limits the compressibility of the outer wire. The outer wire is operatively connectable at a proximal end to a motor for rotating the wire to macerate thrombus.

This application claims priority from provisional application Ser. No.60/628,623, filed Nov. 17, 2004, the entire contents of which areincorporated herein by reference.

BACKGROUND

1. Technical Field

This application relates to a rotational thrombectomy wire for clearingthrombus from native vessels.

2. Background of Related Art

In one method of hemodialysis, dialysis grafts, typically of PTFE, areimplanted under the patient's skin, e.g. the patient's forearm, andsutured at one end to the vein for outflow and at the other end to theartery for inflow. The graft functions as a shunt creating high bloodflow from the artery to the vein and enables access to the patient'sblood without having to directly puncture the vein. (Repeated punctureof the vein could eventually damage the vein and cause blood clots,resulting in vein failure.) One needle is inserted into the graft towithdraw blood from the patient for transport to a dialysis machine(kidney machine); the other needle is inserted into the graft to returnthe filtered blood from the dialysis machine to the patient. In thedialysis machine, toxins and other waste products diffuse through asemi-permeable membrane into a dialysis fluid closely matching thechemical composition of the blood. The filtered blood, i.e. with thewaste products removed, is then returned to the patient's body.

Over a period of time, thrombus or clots may form in the graft. Thrombusor clots may also form in the vessel. One approach to break up theseclots and other obstructions in the graft and vessel is the injection ofthrombolytic agents. The disadvantages of these agents are they areexpensive, require lengthier hospital procedures and create risks ofdrug toxicity and bleeding complications as the clots are broken.

U.S. Pat. No. 5,766,191 provides another approach to breaking up clotsand obstructions via a mechanical thrombectomy device. The patentdiscloses a basket having six memory wires expandable to press againstthe inner lumen to conform to the size and shape of the lumen. Thisdevice could be traumatic if used in the vessel, could denudeendothelium, create vessel spasms and the basket and drive shaft couldfracture.

U.S. Pat. No. 6,090,118 discloses a mechanical thrombectomy device forbreaking up clots. The single thrombectomy wire is rotated to create astanding wave to break-up or macerate thrombus. U.S. Patent PublicationNo. 2002/0173812 discloses another example of a rotational thrombectomywire for breaking up clots. The thrombectomy wire has a sinuous shape atits distal end and is contained within a sheath in a substantiallystraight non-deployed position. When the sheath is retracted, the distalportion of the wire is exposed to enable the wire to return to itsnon-linear sinuous configuration. The wire is composed of stainlesssteel. Actuation of the motor causes rotational movement of the wire,creating a wave pattern, to macerate thrombus. The device of the '812patent publication is effective in atraumatically and effectivelybreaking up blood clots in the graft and is currently being marketed byDatascope, Inc. as the Pro-Lumen* thrombectomy catheter. In the marketeddevice, the wire is a bifilar wire, composed of two stainless steelwires wound side by side with a metal tip and an elastomeric tip at thedistalmost end.

Although the sinuous wire of the '812 publication is effective in properclinical use to macerate thrombus in dialysis grafts, it is not suitedfor use in native vessels. The device is indicated for use in grafts,and if improperly used the wire can kink or knot, and perhaps evenbreak. The wire can also bend, making it difficult to withdraw afteruse, and can lose its shape. Additionally, the wire would be abrasive tothe vessel and the vessel could get caught in the interstices of thewire. It could also cause vessels spasms which can cause the vessel tosqueeze down on the wire which could break the wire. Similar problemswould occur with the use of the device of the '118 patent in nativevessels.

The need therefore exists for a rotational thrombectomy wire which canbe used to clear clots or other obstructions from the native vessels.Such wire could advantageously be used not only in native vesselsadjacent dialysis grafts but for deep vein thrombosis and pulmonaryembolisms.

SUMMARY

The present invention advantageously provides a rotational thrombectomywire for breaking up thrombus or other obstructive material in a lumenof a native vessel.

The present invention provides a rotational thrombectomy wire comprisingan inner core composed of a flexible material and a multifilar outerwire surrounding at least a portion of the inner core. The outer wireincludes at least first and second metal wires wound side by side andhaving a sinuous shaped portion at a distal region. The inner core at adistal portion has a sinuous shaped portion within the sinuous portionof the outer wire. The inner core limits the compressibility of themultifilar wire. The multifilar wire is operatively connectable at aproximal end to a motor for rotating the wire to macerate thrombuswithin the vessel.

In a preferred embodiment, the inner core is composed of nylon material.In another embodiment, the inner core is composed of shape memorymaterial wherein the inner core assumes its sinuous shape in thememorized configuration. In another embodiment, the core comprises atleast two twisted wires of stainless steel.

The thrombectomy wire preferably further includes a polymeric materialsurrounding at least a distal portion of the multifilar wire. In apreferred embodiment, the polymeric material comprises a shrink wrapmaterial attached to the multifilar wire. In another embodiment, thepolymeric material is a coating over the multifilar wire.

The thrombectomy wire preferably comprises a flexible and blunt tippositioned at a distal end.

The inner core can have in one embodiment an enlarged distal end to forma connection portion and a metal tip secured to a distal end of themultifilar wire has a recess to receive the enlarged end of the innercore to frictionally engage the inner core.

In one embodiment, the first and second metal wires are wound togethersuch that the coils of the first wire occupy the space between adjacentturns of the second wire and the coils of the multifilar outer wire havean inner diameter approximately equal to an outer diameter of the innercore.

The present invention also provides a rotatable thrombectomy wire forbreaking up thrombus or other obstructive material in a lumen of avessel comprising a multifilar outer wire including at least two metalwires wound side by side and operatively connectable at a proximal endto a motor for rotating the wire to macerate thrombus. The multifilarwire has a sinuous shaped portion at a distal region. A polymericmaterial surrounds at least a region of the sinuous portion of themultifilar outer wire to block the interstices of the multifilar wire.

In a preferred embodiment, the polymeric material comprises a shrinkwrap material. In another embodiment, the polymeric material is acoating over the bifilar wire.

The present invention also provides a thrombectomy apparatus forbreaking up thrombus or other obstructive material comprising a handle,a sheath, a battery, a motor powered by the battery, and a sinuousthrombectomy wire having at least one wire wound to form a coil and aninner core composed of a material to limit the compressibility of thecoil. The coil has a sinuous portion and surrounds at least a distalregion of the inner core. The inner core has a sinuous portion withinthe sinuous portion of the coil. The sinuous portion of the inner coreand first and second wires are movable from a straighter configurationwithin the sheath for delivery to a sinuous configuration when exposedfrom the sheath.

In a preferred embodiment, a polymeric material surrounds at least adistal portion of the coil to cover the interstices of the coil. In oneembodiment, the core is composed of a shape memory material wherein thememorized position of the core has a sinuous configuration. In anotherembodiment, the core is composed of Nylon. In another embodiment, thecore is composed of at least two twisted wires of stainless steel.

The present invention also provides a method for breaking up thrombus orother obstructive material in a native vessel comprising:

providing a thrombectomy wire having an inner core composed of aflexible material and at least one outer wire surrounding at least aportion of the inner core, the outer wire has a sinuous shaped portionat a distal region and the inner core has a sinuous shaped portionwithin the sinuous portion of the outer wire, and a polymeric materialsurrounding at least a distal portion of the at least one outer wire toblock the interstices of the at least one outer wire;

delivering the wire to the lumen of the native vessel such that thesinuous shaped portions of the inner core and bifilar outer wire are ina more linear configuration within a sheath;

exposing the sinuous portion of the inner core and the at least oneouter wire; and

actuating a motor operatively connected to the thrombectomy wire so thesinuous portion of the at least one outer wire contacts the inner wallof the native vessel to macerate thrombus in the vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiment(s) of the present disclosure are described hereinwith reference to the drawings wherein:

FIG. 1 is a side view in partial cross-section of a first embodiment ofa thrombectomy wire of the present invention shown inside a cathetersleeve for delivery;

FIG. 2 is a schematic view illustrating motorized rotation of the wireand a port for fluid delivery;

FIG. 3 is a schematic side elevational view of the sinuous portion ofthe thrombectomy wire to depict a first embodiment of the inner corepositioned therein;

FIG. 4 is an enlarged cross-sectional view of the distalmost region ofthe rotational thrombectomy wire of FIG. 3;

FIG. 5 is schematic side elevational view of the sinuous portion of thethrombectomy wire to depict a second embodiment of the inner corepositioned therein; and

FIG. 6 is an enlarged side view of the distalmost region of therotational wire of FIG. 5;

FIG. 7 is a schematic side elevational view of the sinuous portion ofthe thrombectomy wire to depict a third embodiment of the inner corepositioned therein; and

FIG. 8 is a cross-sectional view taken along line 8-8 of FIG. 7.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now in detail to the drawings where like reference numeralsidentify similar or like components throughout the several views, FIGS.3 and 4 illustrate a first embodiment of the thrombectomy wire of thepresent invention. The thrombectomy wire, designated generally byreference numeral 10, includes a core 20, a bifilar wire (coil) 30, andshrink wrap 50. The bifilar wire 30 is formed by two stainless steelwires 32, 34, wound together. As shown they are wound side by side sothe cross-sectional area or diameter “a” of the wire fills the spacebetween adjacent turns of the other wire. For example, turns 32 a and 32b are filled by respective turns 34 a, 34 b as shown. Preferably thebifilar wire 30 has a length of about 30 inches and a diameter of about0.030 inches to about 0.040 inches and more preferably about 0.035inches. When used in deeper native vessels, e.g. deep veins of the legsor pulmonary circuit, the wire 30 can have a length of about 52 inches.Other dimensions are also contemplated.

The distal region 16 of the bifilar wire 30 is formed into a sinuous ors-shape to contact the vessel wall as the wire rotates.

Although in the preferred illustrated and described embodiments, theouter wire is a multifilar wire in the form of a bifilar wire (twowires), a different number of wires could be wound to form the outerwire component of the thrombectomy wire of the present invention. In yetanother embodiment the outer wire can comprise a single wound wire.

The bifilar wire 30 is preferably cold formed into an over-formeds-shape. The bifilar wire is heated, for example at about 670 degreesFahrenheit, which removes residual stresses and changes the shape of the“s” so it warps back to its desired shape. This stress relief processmakes the wire more dimensionally stable.

A tip 80, preferably composed of rubber, Pebax, or other elastomericmaterials, is mounted at the distalmost tip of the wire 10 to providethe wire 10 with an atraumatic distal tip to prevent damage to thevessel wall during manipulation and rotation of the wire. A metal lip 60is attached by laser welding or other methods to the distal end of thebifilar wire 30. The metal tip 60 has an enlarged dumbbell shaped head62 to facilitate attachment to tip 80. The flexible tip 80 is attachedby injection molding over the machined tip. Other attachment methods arealso contemplated.

With continued reference to FIG. 4, a core 20 is positioned within thebifilar wire 30 and preferably has an outer diameter E substantiallyequal to the inner diameter D of the coil. The core at a distal portionhas a sinuous shaped portion within the sinuous shaped portion of theouter wire 30, corresponding to and formed by the sinuous shape of outerwire 30. In one embodiment, the core extends the entire length of thebifilar wire 30 and this is shown in the schematic drawing of FIG. 3.The core 20 can alternatively have a length of about 4-5 inches so itextends through the distal linear portion and sinuous portion of thewire 30. That is, in such embodiment, the core extends through theportion of the wire that is exposed from the sheath and used to maceratethrombus. It is also contemplated that the core can extend within ashorter or longer length of the bifilar wire.

The core 20 is composed of a flexible material which will limit thecompressibility of the wire 30 during use. The core in the embodiment ofFIG. 3 is composed of Nylon, and preferably a drawn Nylon monofilament.Other possible materials include, for example, Teflon, polypropylene,PET, and fluorocarbon. The Nylon provides a non-compressible material tolimit the compressibility of the wire 30 during use. That is, as notedabove, the Nylon core preferably has a diameter E to fill the inside ofthe coil 30, e.g. a diameter of about 0.008 inches to about 0.013inches, and preferably about 0.012 inches. (Other dimensions are alsocontemplated.) This enables the coil (bifilar wire) 30 to compress onlyto that diameter. By limiting compressibility it strengthens the wire asit reduces its degree of elongation if it is under torque. It alsoprevents bending or knotting of the wire which could otherwise occur innative vessels. It increases the torsional strength of the wire and alsostrengthens the wire to accommodate spasms occurring in the vessel. Anenlarged distal head, such as ball tip (not shown), can be provided onthe core 20 to fit in a recess of machined tip 60. As an alternative,core 20 can be attached by adhesive at the tip, welded, crimped,soldered or can alternatively be free floating.

The shrink wrap material 50 covers a portion of the bifilar wire 30proximal of the flexible tip 80 to block the interstices of the coil andprovide a less abrasive surface. As shown in FIG. 4, the distal end ofthe shrink wrap abuts the proximal end of the tip 60. The shrink wrapcan be made of PET, Teflon, Pebax, polyurethane or other polymericmaterials. The material extends over the exposed portion of the wire 30(preferably for about 3 inches to about 4 inches) and helps to preventthe native vessel from being caught in the coil and reduces vesselspasms. Alternatively, instead of shrink wrap, a coating can be appliedto the coil formed by the bifilar wire to cover the interstices

FIGS. 5 and 6 illustrate an alternate embodiment of the thrombectomywire of the present invention, designated generally by reference numeral100. Wire 100 is identical to wire 10 of FIG. 1, except for the innercore 120. It is identical in that it has a bifilar wire 130, a shrinkwrap 170, an elastomeric tip 180 and metal, e.g. stainless steel, tip160.

In this embodiment, the core 120 is composed of a shape memory material,preferably Nitinol (a nickel titanium alloy), which has a memorizedconfiguration of a sinuous or s-shape substantially corresponding to thes-shape of the bifilar wire 130. In the softer martensitic state withinthe sheath, core 120 is in a substantially linear configuration. Thisstate is used for delivering the wire to the surgical site. When thewire is exposed to warmer body temperature, the core 120 transforms toits austenitic state, assuming the s-shaped memorized configuration.Cold saline is delivered through the catheter during delivery tomaintain the core 120 in this martensitic state; the warming occurs byexposure to body temperature to transform the core 120 to the memorizedstate. Such memorized s-shape helps maintain the s-shape of the bifilarwire 130 during use. Cold saline can also be delivered to the core 120at the end of the procedure to facilitate withdrawal.

The Nitinol core 120, like the Nylon core 20, is not compressible so itwill also limit the compressibility of the bifilar wire 130. The Nitinolcore 120 also will increase the stiffness of the wire 100, therebyreducing the chance of knotting and kinking and increase the strength ofthe wire to accommodate any spasms in the vessel. Its shape memory helpshold the amplitude of the bifilar wire 130 during use to maintain itsforce against the clot for maceration upon rotation. It preferablyextends about 4-5 inches so it extends through the distal linear portionand sinuous portion of the wire 130, terminating at end 122. Alternatelyit can extend a shorter or longer length within the wire 130, or eventhe entire length as shown in the schematic view of FIG. 5. Itpreferably has an outer diameter of about 0.008 inches to about 0.013inches, and more preferably about 0.012 inches, corresponding to theinner diameter of the coil. Other dimensions are also contemplated.

In another embodiment, a stainless steel braid, cable, or strand ofwires twisted together provides the inner core member to limitcompressibility of the coil (bifilar wire) and provide increasedstiffness, strength and other advantages of the core enumerated above.This is shown in the embodiment of FIGS. 7 and 8 where wire 200 hasinner core 220 of seven twisted stainless steel wires. A differentnumber of twisted wires is also contemplated. The other elements of thewire 200, e.g., outer bifilar wire 230, metal tip 260, tip 280 shrinkwrap 250, etc., are the same as in wires 10 and 100 described herein.

The rotational thrombectomy wires 10, 100 and 200 of the presentinvention can be used with various thrombectomy catheters to maceratethrombus within the vessel. The rotational thrombectomy wire 10 (or wire100 or 200) is contained within a flexible sheath or sleeve C of acatheter as shown in FIG. 1. Relative movement of the wire and sheath Cwill enable the wire 10 to be exposed to assume the curved (sinuous)configuration described below to enable removal of obstructions, such asblood clots, from the lumen of the vessel.

A motor powered by a battery is contained within a housing to macerateand liquefy the thrombus into small particles within the vessel lumen.This is shown schematically in FIG. 2. Wire 10 (or 100 or 200) isoperatively connected to the motor. Operative connection encompassesdirect connection or connection via interposing components to enablerotation when the motor is actuated. The curved regions of the wire 10or (100 or 200) are compressed so the wire (including the distal region16, 116 or 216, respectively) is in a substantially straight or linearnon-deployed configuration when in the sheath C. This covering of thewire 10 (or 100 or 200) by sheath C facilitates insertion through anintroducer sheath and manipulation within the vessel. When the flexiblesheath C is retracted, the wire is exposed to enable the wire to returnto its non-linear substantially sinuous configuration for rotation aboutits longitudinal axis within the lumen of the vessel.

Fluids, such as imaging dye can be injected through the port D into thelumen of the sheath C in the space between wire 10 (or 100 or 200) andthe inner wall of the sheath C, and exiting the distal opening to flowinto the vessel. This imaging dye provides an indication that fluid flowhas resumed in the vessel. The lumen of the sheath can also receive coldsaline to cool the Nitinol core 120 as described above.

The rotational thrombectomy wires 10, 100 and 200 of the presentinvention can also be used with the thrombectomy catheters having one ormore balloons such as the balloon described in the '812 publication. Thewires 10, 100 and 200 can further be used with other thrombectomycatheters.

While the above description contains many specifics, those specificsshould not be construed as limitations on the scope of the disclosure,but merely as exemplifications of preferred embodiments thereof. Thoseskilled in the art will envision many other possible variations that arewithin the scope and spirit of the disclosure as defined by the claimsappended hereto.

1-20. (canceled)
 21. A rotational thrombectomy wire for breaking upthrombus or other obstructive material comprising an inner core, firstand second outer wires wound over the inner core, a polymeric materialover a first portion of the outer wires, a metal tip positioned over asecond portion of the outer wires, and a flexible blunt tip positionedover the metal tip and extending distally therefrom and extendingdistally of the polymeric material.
 22. The thrombectomy wire of claim21, wherein the inner core is composed of stainless steel.
 23. Thethrombectomy wire of claim 21, wherein the inner core is composed ofmultiple twisted wires of stainless steel.
 24. The thrombectomy wire ofclaim 21, wherein the polymeric material is a coating over the first andsecond outer wires to block the interstices of the outer wires.
 25. Thethrombectomy wire of claim 24, wherein the polymeric material comprisesa shrink wrap material attached to the first and second outer wires toblock the interstices of the outer wires.
 26. The thrombectomy wire ofclaim 21, wherein the first and second outer wires are wound togethersuch that the coils of the first wire occupy the space between adjacentturns of the second wire.
 27. The thrombectomy wire of claim 21, whereinthe metal tip has a dumbbell shaped region.
 28. The thrombectomy wire ofclaim 27, wherein the flexible blunt tip is injection molded over thedumbbell shaped region of the metal tip.
 29. The thrombectomy wire ofclaim 25, wherein the shrink wrap is proximal of the flexible tip. 30.The thrombectomy wire of claim 29, wherein the shrink wrap abuts aproximal portion of the metal tip.
 31. The thrombectomy wire of claim26, wherein the inner core comprises a plurality of twisted wires. 32.The thrombectomy wire of claim 21, wherein the metal tip has anincreased height region forming a first smaller height region distal ofthe increased height region and a second smaller height region proximalof the increased height region.
 33. The thrombectomy wire of claim 32,wherein the flexible blunt tip is injection molded over the increasedand smaller height regions of the metal tip.
 34. The thrombectomy wireof claim 21, wherein the inner core is positioned within alongitudinally extending opening in the metal tip.
 35. The thrombectomywire of claim 21, wherein the inner core and first and second outerwires are positioned within a longitudinally extending opening in themetal tip.
 36. The thrombectomy wire of claim 21, wherein a proximal endof the flexible blunt tip is spaced axially distally from a distal endof the polymeric material.